Extraction of chitin/chitosan from shrimp wastes and application of irradiated chitosan as an anti-bacterial agent

Abstract

Chitin, the second abundant naturally occurring polysaccharide, is found in the exoskeleton of insects and crustaceans (e.g. shrimps, lobsters, crabs, turtles etc.) and cell wall of fungi. The present investigation was carried out to extract chitin from shrimp wastes, convert chitin into chitosan, and evaluate the practicality of chitin-chitosan as an anti-microbial agent. Chitin was extracted from shrimp wastes. The conversion rate achieved was 28.26%. Both acetic acid and citric acid were found to be suitable for the solubility of chitosan, but acetic acid seemed to be a relatively better solvent for chitosan. Solubility was increased when chitosan was irradiated with 80 kGy gamma irradiation dose or more. Commercial chitosan and prepared chitosan were tested against Staphylococcus aureus, Escherichia coli, and Bacillus sp. isolated from spoiled mango and papaya. Experiments were conducted on radiation-induced enhancement of antimicrobial activity of chitosan. 0.01% chitosan (both prepared and commercial) was found to decrease the bacterial load of all the bacterial species and chitosan irradiated with 80 kGy or more had better antibacterial activity in this concentration, although this chitosan concentration was not effective enough to tota1 elimination of bacterial load. Chitosan concentration of 0.025% was found to be effective for total elimination of the bacteria.